1. Field of the Invention
This invention relates generally to wireless communication input circuits in semiconductor devices. Specifically the present invention relates to clamping the input voltage which may be induced in the presence of strong RF fields for the purpose of preventing damage to electronics connected to the input circuit.
2. Description of the Prior Art
A wireless communication input circuit has two desirable characteristics. First, a high impedance input is needed so that power is not dissipated in the input circuit. Second, a low impedance over-voltage clamp is required so that electronic circuitry downstream of the input circuit is protected from high voltages which are induced in the presence of strong RF fields.
The current state of the art describes voltage clamps which are implemented by means of zener diodes. While there are numerous limitations to zener diodes, a primary concern are controlling fabrication parameters in RF input circuits which are implemented on a single, monolithic integrated circuit. Zener diodes also are characterized by difficulty in creating symmetrical clamping for positive and negative voltages.
Therefore, a need existed to provide a voltage clamp that will provide symmetrical positive and negative voltage clamping.